Combustible carbonaceous material, in the form of briquettes, is the fuel of choice for cooking various kinds of meat. Cooking meat in this manner is generally referred to as barbecuing. In the process of barbecuing, meat is placed over a source of heat and the meat is cooked in such a manner that various smoke and vapors contact the meat thereby giving the meat its unique barbecue flavor. The smoke and vapors are often times produced by the fats of the meat or barbecue sauce, which when the fat or sauce contact the source of heat they are vaporized and contact the meat to produce the pleasant taste. In addition, sometimes the source of the heat itself may produce a smoke which flavors the meat being cooked. Combustible carbonaceous material, such as charcoal, peat, coal, etc., which has been compressed into the form of a briquette and has sufficient strength to maintain its briquette shape is normally used to barbecue meat.
As is known in the art, charcoal is produced by the destructive distillation or limited combustion (i.e. in the absence of oxygen) of wood, lignites, coal and other petroleum derivatives. The charcoal thus produced is then compressed into briquettes for use as a barbecue fuel. However, other combustible carbonaceous material such as raw coal and peat have also been compressed, formed into briquettes and used as barbecue fuel.
In general, barbecue briquettes are made by adding a binder, such as starch, to, e.g. charcoal, and, perhaps an oxidizing agent, as well as water, and the mixture is compressed and formed into briquettes on a briquetting machine, consisting of two rolls, each with an impression of half of the briquette on the roll, so that when the two rolls are brought together under pressure the material contained therein is squeezed into the pockets to form the familiar briquette-like shape (i.e. a shape similar to a small brick). In general, if charcoal is used, it will have approximately 20% and 30% water and from 8% to 10% of a bonding agent such as starch. After this mixture is formed into the familiar briquette shape, the briquettes are subsequently dried to remove essentially all of the moisture (perhaps the final product will contain no more than 4% moisture) and are then ready for consumer use as a barbecue fuel.
One of the early patents issued relating to the charcoal briquette field is U.S. Pat. No. 1,590,706 which discusses prior art bonding agents for charcoal which, according to the patent, include pitch, chalk, clay, cement, and plaster of paris. The improvement disclosed in this patent is a new bonding agent which is added to finely divided particles of coal to form a briquette possessing the desired properties. According to column 2 of this patent, the patentee uses a "crude soluble phosphate extract obtained by treating phosphatic rock or similar phosphate material with sulphuric acid".
Another early patent is U.S. Pat. No. 1,618,029 which uses a rather wide variety of various bonding agents for coal. The binding agents "stabilized" by the addition of an acid such as sulphuric acid. Another patent which discloses using an acid in conjunction with a binding agent (in this instance starch) is U.S. Pat. No. 2,890,945 which discloses that the addition of acetic acid, to starch and charcoal, is useful in forming a coal briquette.
A more recent innovation in briquettes is disclosed in U.S. Pat. No. 3,485,599 in which certain types of oxidizing agents are added to the charcoal briquette in order to render the briquette rapidly ignitable. In addition to the addition of an oxidizing agent such as sodium nitrate, a retarder is also added to prevent the charcoal briquettes from being spontaneously combustible. This retarder is added in small amounts, relative to the oxidizing agent, and may be a bentonite clay "composed principally of aluminum silicates with some magnesium and iron". In addition, this patent uses a conventional starch binder.
Another relatively recent innovation relating to briquettes is disclosed in U.S. Pat. No. 3,836,343. According to this patent, the normal binding agents utilized in producing charcoal briquettes are pitch and bitumen and such binding agents generate large amounts of smoke. Accordingly, the object of the U.S. Pat. No. 3,836,343 is to produce a smokeless briquette. This is allegedly accomplished by replacing the known binding agents with a binding agent comprising a butadiene acrylonitrile copolymer. This copolymer is present in an amount of from 0.5% to 2%, by weight.